COMPLEX HEATING, COOLING, AND HEAT RECOVERY PLANT … · •Energy storage for solar hot water or waste heat recovery ThermalStorage:ChilledWater ThermalStorage:Ice. AFFILIATED ENGINEERS,

AFFILIATED ENGINEERS, INC. 1

COMPLEX HEATING, COOLING, AND HEAT RECOVERY PLANT MODELING

Energy Trust of Oregon

Building Energy Simulation Forum

04/18/2018

Lyle Keck, PE, LEED AP BD+C

Building Performance Consultant


Agenda

Plant modeling basics using EnergyPlus (E+)• ‘Complex’ hydronic plant modeling

• E+ plant loop structure and equipment

• E+ plant loop controls & Energy Management System (EMS)

Simulation workflow approach

• Model setup and input file creation

• Pre/post processing, model diagnostics

Case studies• OHSU – CHH South, Block 28 & 29 (Portland, OR)

• PHSA – Teck Acute Care Centre (Vancouver, BC)

• Seattle Children’s Hospital – Building CARE (Seattle, WA)


EnergyPlusPlant Loop Modeling


Why EnergyPlus?Limited Flexibility

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Why EnergyPlus?

Flexibility to build hydronic loops to simulate the energy performance as designed and engineered

Detailed objects for many real world equipment and components• Boilers, chillers, heat pumps

• Thermal storage tanks (HW, CHW, mixed/stratified, ice)

• Loop-to-loop objects, heat exchangers and heat pumps

Robust controls

• Many types of setpoint managers, load operation schemes

• Custom EMS controls


Plant Loop - StructureSupply Side Demand Side

EnergyPlus has 2 main types of loops in the HVAC simulation• Air loop and plant loop

• Plant loop uses a liquid fluid as the transport medium

Each loop is broken up into 2 half-loops

• Supply side and demand side

• Demand side equipment places a load on the supply side primary equipment

• The supply side operates to meet a specific load and flow condition

• User specified rules for how that load is distributed to supply side equipment


Plant Loop - StructureINLET OUTLET / INLET OUTLETSupply Side Demand Side

Each half-loop has an inlet and outlet

Loop pump is typically placed as first object on supply side inlet

• Placing a pump on the demand side inlet will simulate primary-secondary systems

• ‘Branch pump’ can be placed in parallel section of a branch (chiller/boiler pump, etc.)

pump


Plant Loop Basics - Structure

Components• Nodes (stores properties of the loop at that location)

• Branches (one or more objects linked together in series)

• Splitter/mixer (allow branches to be setup in parallel)

Structure• Within any single branch, objects can only be in series

• Each half-loop may only have 1 splitter and 1 mixer

• Branches may be in parallel only between the mixer and splitter

• Good practice to have a splitter and mixer even if all objects are in series


Plant Equipment – Commonly Used Objects

Chiller:Electric:EIR

• Air-cooled or water-cooled

• Heat recovery only available with water-cooled condenser*

Boiler:HotWater

DistrictCooling

DistrictHeating



HeatPump:WaterToWater• 4-pipe hydronic (hot, cold)

• Two models, EquationFit:Cooling and EquationFit:Heating

• Object only controls to one mode (heating or cooling), other mode is always passive

CentralHeatPumpSystem• 6-pipe hydronic (hot, cold, source)

• Made of multiple ChillerHeater objects

• 5 modes of operation

Heating only, cooling only, balanced heat recovery, heat recovery with trim cooling, heat recovery with trim heating

User not able to actively control mode of operation*



WaterHeater:Mixed• Hot water storage tank

• Can be standalone or coupled with other objects…

• WaterHeater:HeatPump (often used to approximate plant loop air-to-water HPs by minimizing tank volume)

• Energy storage for solar hot water or waste heat recovery

ThermalStorage:ChilledWater

ThermalStorage:Ice


Plant Loop Controls

Control Objects• SetpointManagers

• AvailabilityManagers

• PlantEquipmentOperationSchemes

• Energy Management System (EMS)


Plant Loop Controls





Description

Place a calculated or scheduled setpoint value on the setpoint node

Setpoints are then used by plant loops as a goal for their control actions

Examples• SetpointManager:Scheduled

• SetpointManager:OutdoorAirReset

• SetpointManager:ReturnTemperature


Plant Loop Controls





Description

Access data from node and make a decision on whether a plant loop or equipment should be on or off

Output is an availability status flag

Loop pump then takes action of turning loop on or off – availability manager will overrule the pump on/off schedule

Examples• AvailabilityManager:Scheduled

• AvailabilityManager:DifferentialThermostat

• “ ”:High/Low Temperature Turn On/Off


Plant Loop Controls





Description

Once loop load is calculated from demand side and loop setpoint, the load needs to be allocated to the supply equipment according to user input.

Overall operation scheme assigns priorities to multiple control schemes that may be assigned to a loop (list order defines priority)

If control scheme is unavailable, control will move to the next highest priority

Operation scheme links to a list of equipment and uses the plant loop load distribution scheme to dispatch load to equipment


Plant Loop Controls





Uncontrolled• If the loop runs, the equipment will also run to full

capacity

Load based control schemes • HeatingLoad, CoolingLoad

• Defines load range and which equipment can operate for each range

• Load is dispatched according to load distribution scheme (sequential, uniform, PLR or load range)

ComponentSetpoint• Sequences plant components based on the outlet

temperature of individual equipment

• Each piece of equipment must have its own setpoint that is different from loop setpoint


Plant Loop Controls





“The Book of Erl”

Description

EMS provides a way to develop custom control and modeling routines for E+

Provides high-level supervisory control to override selected aspects of E+ simulations

Access sensor data and use this data to direct control actions

Concept is to emulate the types of control possible with DDC building automation systems in real buildings


Plant Loop Controls - EMS

EMS:Sensor• Declares a variable. Used to get information from

somewhere else in the model to use in control calculations.

• Generally uses normal E+ output variables

EMS:Actuator

• EMS initiates control actions by changing the value of this variable.

• Actuators override things in E+. Normal operation resumes when actuator is set to Null.

• Can be scheduled value, on/off status, flow rate, load dispatch, node property, etc.

EMS:Program• Contains control logic (code) to be executed

• Uses simple if/then/else/set statements, functions and expressions to

EMS:ProgramCallingManager

• Defines when in the simulation, and/or timestep, EMS programs are executed

• Also defines when EMS programs are executed relative to other EMS programs

Global/Output/Internal Variables• Another means of accessing and reporting variables

for use in EMS


Plant Loop Controls - EMS


SimulationWorkflow


Simulation Workflow Approaches

Model setup and input file creation• EnergyPlus IDF Editor

• OpenStudio

Pre & Post Processing

• Data transfer and calculation

• Model diagnostics


Simulation Workflow – Model Setup

EnergyPlus IDF Editor• ‘GUI’ that is distributed with E+

• No visual representation of system layout until successful setup and simulation

• Many objects to manage for each piece of equipment….



To add 1 boiler in IDF editor:• Boiler:HotWater

• Inlet Node, Outlet Node

• Branch

• BranchList

• Connector:Splitter

• Connector:Mixer

• PlantEquipmentList

• May require more….



OpenStudio (OS)• Collection of tools to support

whole building modeling using E+ simulation engine

• OS Application (GUI)

• OS Software Development Kit (SDK / API)

• OS Measures (scripts)

• Other tools including SketchUp plugin for geometry, parametric analysis tool, Radiance



OpenStudio (OS)• Use OS Application to quickly setup plant

loops

• Visual interface that holds E+ loop structure and general ruleset

• Adding components to loop does a lot of the ‘heavy lifting’ setup and coordination/management

• Export E+ input file (IDF) for further manipulation if needed

• Measure to automate setup and bake-in best practices



Custom workflows with OpenStudio API• Use OS SDK to create custom tools that quickly generate E+ plant models


Simulation Workflow – Pre Processing

Plant model can be separate model from whole building model• Multiple buildings fed by a central district or campus plant

• OpenStudio (or other) whole building model and EnergyPlus plant model

• May be easier to setup and troubleshoot plant model in isolation, faster simulation time

• Preference and discretion of modeler

LoadProfile:Plant Object

• Used to transfer loop load/flow information from whole building model to plant model

• Can reference hourly CSV file, or reference manual schedules in E+

• Hourly data for Load [W], Flow Rate [m3/s], Flow Rate Fraction [0-1]

Create hourly variables in whole building model

Use loop design temperature difference and peak hourly load to define flow rates (peak & hourly)

Flow rate fraction is a normalized value of hourly flow rate to peak flow rate


Simulation Workflow – Pre Processing

Data Transfer

Use custom python script to automate this process, which does the following…

• Run OS whole building simulation

• Query results file (SQL) to pull out hourly loop variables

• Calculate peak/hourly/normalized flow rates based on loop design temperature difference

• Write hourly loop information to CSV file referenced by LoadProfile:Plant object

• Run E+ plant simulation

• Query results file (SQL) and combine results from whole building model and plant model as desired


Simulation Workflow – Post Processing

Model Diagnostics

Model results are used to ensure the model is operating as intended and support design

EnergyPlus tabular results

• HTML file and web browser

• CSV / excel

EnergyPlus hourly results• xEsoView

• DView

• CSV / excel

OpenStudio results

• E+ output files (above)

• OS application

• DView now packaged w/ OS



Model Diagnostics• Custom python based dashboards

• Query tabular and hourly results from E+ output file (SQL) and create model diagnostic reports



Model Diagnostics• Visualize design inputs, sizing inputs & results,

tabular results and hourly data side-by-side

• Calculate key performance metrics to assess operational efficiency

• Report key metrics to inform design and write results to integrate with design workflow tools

• Intelligent sorting and binning of data

• Flexible – query model and grab appropriate results, automatically adapts to changes in number of objects & components

• Interactive – scale, zoom, hover, save image with a single click


Plant ModelingCase Studies


Case Studies

Oregon Health & Sciences University – Center for Health and Healing South (OHSU CHH South)• Portland, OR

• Two buildings (B28 & B29) with common central plant

• Heat recovery chiller, exhaust air heat recovery

• ETO incentive modeling

Provincial Health Services Authority – Teck Acute Care Centre (TACC)

• Vancouver, BC

• Air source heat pump

• BC Hyrdo incentive modeling

Seattle Children’s Hospital – Building CARE (SCH CARE)

• Seattle, WA

• Thermal storage

• Solar hot water collectors


OHSU - Center for Health & Healing South (CHH South)

Client:• Oregon Health & Sciences University

Location:• Portland, OR

Size:• 330,000 ft2 (Block 29)

• 120,000 ft2 (Block 28)

Building Program:

• Outpatient ambulatory surgery center, outpatient clinical services, medical office (Block 29)

• Conference center, patient family lodging, parking (Block 28)

Status:• Under construction

ZGF Architects


OHSU – Center For Health & Healing South

Modeling Services:• Design performance analysis

• Utility incentives (ETO)

• LEED certification

Central Plant:

Located in B29, provides HHW and CHW to B28 & B29, also provides CHW to B25 (CHH North)

• Condensing gas fired boilers

(4x) 5,600 MBH

• High efficiency water-cooled chillers & cooling towers

(2x) 1,000 ton centrifugal chillers

• Water-to-water heat recovery chillers (HRCs) w/ exhaust air heat recovery coils

(2x) 250 ton

90,000 CFM of exhaust air recovery coils

BLOCK 29

BLOCK 28



Modeling approach

Separate whole building models for B28 and B29

Combined plant model with hourly load profiles from B28, B29 and B25

Python script to…• automatically create HHW and CHW load profiles from whole building models

• calculate and create ‘false cooling’ heat recovery load profile based on design inputs and hourly results

• Runs whole building models, creates load profiles, runs plant model, combine results

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B29 CentralPlant



Exhaust Air Heat Recovery w/ HRCs:• Utilize building exhaust as a heat source (70-75F)

for a super efficient form of heat pump heating

~3X more efficient than gas-fired boilers

Boiler COP = 0.9

HRC Heating COP = 3.0 - 3.5

• Capture heat leaving the building and transfer/reuse that heat at a higher grade to HHW loop

• Ability to meet preheat, reheat, and domestic water heating demands

• Operate when heating dominant:

HRC meets simultaneous heating/cooling demand first

Then engage ‘false cooling’ heat recovery coils to provide trim heating



EnergyPlus Plant Model

CHW loop

CW loop

HHW loop

chillers/HRC

cooling towers

cooling load profiles

chiller connections

heating load profiles

HRC & boilers



EnergyPlus Objects:

• Boiler:HotWater

• Chiller:Electric:EIR

• CoolingTower:VariableSpeed

• HeatPump:WaterToWater:EquationFit:Cooling

• EnergyManagementSystem:Program (and associated components)

EMS Control Logic:

• HeatPump:WaterToWater:EquationFit:Cooling only controls to cooling demand, condenser heat is passively dumped to HHW loop regardless of demand (results in overheating of loop)

• EMS is used to optimize and control HeatPump based on both CHW and HHW loop demands. Intelligently dispatch loads to HRC, chillers, and boilers.

At every time step…

• EMS reads HHW and CHW loop demands, calculates simultaneous load

• Calculates heating and cooling output of HeatPump based on load and input power at that operating point

• Determines load to be placed on HeatPump based on limiting factor (heating/cooling output)

• Calculates ‘cooling’ dispatch to HeatPump based on desired heating/cooling output

• Takes remaining HHW and CHW demands and dispatches to trim boilers and chillers



ETO Incentive Modeling Approach:

B28 and B29 as 2 separate ETO projects

Plant savings captured under B29 project

Gas as ‘primary’ heating source with heat recovery in both models.

Baseline plant:• Boilers

• Water-cooled chillers

• Condenser water heat recovery (sized for 30% of peak heat rejection load at design conditions)



Plant Modeling Takeaways

• Python script to integrate whole building models with separate plant model

• Python script to create hourly profile for HRC exhaust air heat recovery

• EnergyPlus EMS program to control operation of HRC and optimize based on heating demand and cooling demand simultaneously

Plant Modeling Results

• Energy savings: 49 EUI [kBtu/sf-yr]

• Annual energy cost savings: $210,000

• ETO measure incentive: $170,000

• Annual water savings: 1.7M gallons


Teck Acute Care Centre

Client:• Provincial Health Services Authority

Location:• Vancouver, BC

Size:• 675,000 ft2

Building Program: • Acute care inpatient & outpatient services

• Emergency department, med/surg inpatient units, medical imaging, oncology/hematology, PICU/NICU, labor & delivery

Status:

• Open & operating as of Fall 2017

• Monitoring & verification of energy targetAffiliated Engineers, Inc.



Modeling Services:

Design performance analysis (energy target)

Utility incentives (BC Hydro)

LEED certification

Central Plant:

• Water-to-water heat recovery chillers w/ exhaust air heat recovery coils

(4x) 85-ton modules

• Air-cooled heat recovery chillers(1x) 275-ton

• Air-source heat pump(8x) 30-ton modules

• High efficiency air-cooled chillers(3x) 400-ton

• District heating



Plant Order of Operations:

Cooling• Process cooling met by water-water HRC

• First stage of AHU cooling provided by air-cooled HRC (simul. heating/cooling)

• Second stage AHU cooling provided by air-cooled chillers (trim)

Heating

• First stage provided by water-water HRC and air-cooled HRC (simul. heating/cooling)

• Second stage provided by air-source heat pumps located in building relief (heat pump heating)

• Third stage provided by district heat (trim)



EnergyPlus Plant Model:

CHW loop

Process CHW loop

Heat recovery loop

HHW loop

Air-source HP

air-cooled HRC

air-cooled chillers

water-water HRC

CHW load profile

process CHW load profile

heat exchanger

HHW load profileheat recovery heat exchanger, boilers



EnergyPlus Objects:

• District:Heating



• WaterHeater:Mixed

• WaterHeater:HeatPump:PumpedCondenser

• Coil:WaterHeating:AirToWaterHeatPump:Pumped

• HeatExchanger:FluidToFluid


WaterHeater:Mixed Object:

Used to approximate air-to-water heat pumps located in building relief airstream*

• Set storage tank volume to 1 gallon (virtually no thermal storage)

• Use heat pump with air-to-water coil

• Schedule evaporator nodes of heat pump coil to equal relief air conditions

*native EnergyPlus air-to-water HP is only for Zone HVAC use, not plant loop



BC Hydro Incentive Modeling Approach:

Unique methodology to baseline plant regarding fuel switching

• Baseline heating plant includes a mix of electric air-to-water heat pumps and gas-fired boilers (matches fuel source mix of proposed heating equipment)

• Baseline heat pumps sized and controlled to match the proportion of annual load met by electricity vs. gas in the proposed model.

Great energy modeling guidelines including detailed modeling procedures and equipment performance tables that are not well defined in reference codes/standards




• Use of WaterHeater:Mixed object to approximate air-to-water heat pumps connected to plant loop

• For complex equipment control and heat recovery, consider using a separate plant loop as intermediate between CHW and HHW loops

• Innovative approach to fuel switching and baseline heating plant modeling for BC Hydro


• Annual energy cost savings: $185,000

• BC Hydro measure incentive: $600,000


Seattle Children’s Hospital – Building CARE

Client:• Seattle Children’s Hospital

Location:• Seattle, WA

Size:• 300,000 ft2

Building Program: • Acute care inpatient & outpatient services

• Operating rooms/interventional suites, diagnostic and therapeutic services, inpatient unit, ambulatory clinics, infusion, sterile processing, admin/support

Status:

• In designZGF Architects



Modeling Services:

Design performance analysis (energy target)

Code compliance (City of Seattle)

Utility incentives (SCL/PSE)

LEED certification

Central Plant:• Water-to-water heat recovery chillers

w/ exhaust air heat recovery coils(1x) 250-ton

• Air-cooled chillers(5x) 525-ton

• Solar thermal array & HW storage(95) Evacuated tube collectors

(4x) 1,250 gallon HW storage tanks

• Condensing gas-fired boilers(5x) 3,400 MBH



CHW loop

HHW loop

Solar HW loop

water-water HRC

air-cooled chillers

HW storage tanks solar HW collectors

HW storage tank

water-water HRC

boilers

cooling load profiles

heating load profiles

EnergyPlus Plant Model:



EnergyPlus Objects:


• Boiler:HotWater


• WaterHeater:Mixed

• SolarCollector:FlatPlate:Water


WaterHeater:Mixed and Thermal Storage:• Storage tank ‘use’ size typically autosizes

reasonably, but ‘source’ side is bad for autosizing because there is no demand (hard sizing is best here)

• AvailabilityManager:DifferentialThermostat can be used to schedule equipment ON/OFF based on temperature difference between 2 nodes

• PlantEquipmentOperation:ComponentSetpoint can be used to sequence plant equipment based on outlet temperatures for individual equipment


Heating Demand

Cooling Demand

Heating Demand (Trim)

Simultaneous Demand

Cooling Demand (Trim)

Simultaneous Demand


Boilers

HRC: Simultaneous Heat/Cool

Air-Cooled Chillers

HRC: ‘False Cooling’ Heat Recovery

Solar Water Heating

HRC: Simultaneous Heat/Cool

Air-Cooled Chillers

Boilers




• WaterHeater:Mixed and SolarCollector:FlatPlate:Water used to simulate evacuated tube solar HW panels with HW thermal storage

• Good practice to hard-size EnergyPlus ‘source’ side components

• Explore different combinations of availability managers, operation schemes, and EMS controls to achieve desired operation


Boilers & Chillers • 43 EUI [kBtu/sf-yr]

Condensing gas boilers & premium efficiency air-cooled chillers

Boilers, Chillers, HRC (simul. only)• 33 EUI [kBtu/sf-yr]

• 23% savings

Boilers, Chillers, HRC (simul. + false cooling), solar HW

• 11 EUI [kBtu/sf-yr]

• 74% savings


QUESTIONS?

Lyle Keck, PE, LEED AP BD+C

[email protected]

aeieng.com

AEI/Affiliated Engineers, Inc.

@AEITweets

Documents

COMPLEX HEATING, COOLING, AND HEAT RECOVERY PLANT … · •Energy storage for solar hot water or waste heat recovery ThermalStorage:ChilledWater ThermalStorage:Ice. AFFILIATED ENGINEERS,